KPA500 Buzz SOLVED

[WD6DBM]

My KPA500 #274 worked fine with the yellow wire installed, but the voltage was a bit low (56-year old house) and output on 6M was also a tad low.  I wired it for 220v.  Since I use it for meteor scatter on 6m, I really wanted full output.  But when I switched to the red wire, I got a terrible buzz.  I don't mean a slight buzz, I mean a buzz on the order of an arc welder running at full tilt.  A buzz that was louder than when the pole pig across the street caught fire.  A buzz far too loud to be tolerated in a nice, quiet, Elecraft-equipped shack. 
 
I tried repositioning the transformer a number of times to no avail.  I finally contacted Gary at Elecraft support, and working with him got the problem solved.  Here's what I did:
 
1)  Replaced the transformer hold-down bolt that was threaded only at the top with a bolt that was threaded all the way down.  I installed this according to the new procedure in the KPA500 assembly manual (this is now shipped with all KPA500s). 
 
2)  I zip-tied together a number of the wires so that they were not contacting the transformer or the top of the case any more than was necessary.
 
3)  I used a torque wrench to install the transformer to the correct spec in the manual.
 
I'm not sure what fixed it, but the buzz is now down to a very slight, almost unnoticeable level.  I have silent QRO on CW.  Luxury.   
 
I offer this for anyone with an early KPA500 with a loud buzzing problem.  When this thread was active there seemed to be some confusion about what was a normal buzzing level.  Wayne stated that some buzz was normal, but I am sure that others experienced this extremely loud buzz that is not normal.  I never saw a resolution of this thread, so if I missed it my apologies.
 
73,
 
Eric WD6DBM 
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[Johnny Siu]

Hello Eric,
 
All these have already been covered in the latest manual with new mounting hardware for the transformer.  I did the same as you and the problem solved.

TNX & 73,


Johnny VR2XMC


________________________________
 從︰ eric norris <[hidden email]>
收件人︰ "[hidden email]" <[hidden email]>
傳送日期︰ 2011年12月3日 (週六) 8:00 PM
主題︰ [Elecraft] KPA500 Buzz SOLVED
 
My KPA500 #274 worked fine with the yellow wire installed, but the voltage was a bit low (56-year old house) and output on 6M was also a tad low.  I wired it for 220v.  Since I use it for meteor scatter on 6m, I really wanted full output.  But when I switched to the red wire, I got a terrible buzz.  I don't mean a slight buzz, I mean a buzz on the order of an arc welder running at full tilt.  A buzz that was louder than when the pole pig across the street caught fire.  A buzz far too loud to be tolerated in a nice, quiet, Elecraft-equipped shack. 
 
I tried repositioning the transformer a number of times to no avail.  I finally contacted Gary at Elecraft support, and working with him got the problem solved.  Here's what I did:
 
1)  Replaced the transformer hold-down bolt that was threaded only at the top with a bolt that was threaded all the way down.  I installed this according to the new procedure in the KPA500 assembly manual (this is now shipped with all KPA500s). 
 
2)  I zip-tied together a number of the wires so that they were not contacting the transformer or the top of the case any more than was necessary.
 
3)  I used a torque wrench to install the transformer to the correct spec in the manual.
 
I'm not sure what fixed it, but the buzz is now down to a very slight, almost unnoticeable level.  I have silent QRO on CW.  Luxury.   
 
I offer this for anyone with an early KPA500 with a loud buzzing problem.  When this thread was active there seemed to be some confusion about what was a normal buzzing level.  Wayne stated that some buzz was normal, but I am sure that others experienced this extremely loud buzz that is not normal.  I never saw a resolution of this thread, so if I missed it my apologies.
 
73,
 
Eric WD6DBM 
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[N5GE]

I had a loud fan in my KPA500.

I contacted Gary and he had them send me a new fan and all was well.

Merry Christmas to all of the folks at Elecraft.

Excellent customer service all the way around!

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

"If somebody has a bad heart,
they can plug this jack in at
night as they go to bed and it
will monitor their heart
throughout the night. And the
next morning, when they wake up
dead, there'll be a record."

--Mark S. Fowler, FCC Chairman


On Sat, 3 Dec 2011 04:00:04 -0800 (PST), eric norris <[hidden email]>
wrote:

>My KPA500 #274 worked fine with the yellow wire installed, but the voltage was a bit low (56-year old house) and output on 6M was also a tad low.  I wired it for 220v.  Since I use it for meteor scatter on 6m, I really wanted full output.  But when I switched to the red wire, I got a terrible buzz.  I don't mean a slight buzz, I mean a buzz on the order of an arc welder running at full tilt.  A buzz that was louder than when the pole pig across the street caught fire.  A buzz far too loud to be tolerated in a nice, quiet, Elecraft-equipped shack. 
[snip]

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